Let All Rivers Run to the Sea

Alexander J. E. English
Monday, October 21, 2013
As seen from space, Ghana's Volta Dam reservoir is the largest on Earth at 8,482 sq km, or ten times the size of Tokyo.
As seen from space, Ghana's Volta Dam reservoir is the largest on Earth at 8,482 sq km, or ten times the size of Tokyo.
Photo courtesy of Wikipedia

Climate Change Mitigation through Reservoir Removal & Watershed Management

 A paper by Alexander J. E. English, J.D., M.E.L.P.
Certificate in Water Resources Law 
Vermont Law School, ‘13 

Executive Summary

There should no longer be any reasonable doubt that Earth is undergoing a dramatic climactic shift. Since the Industrial Revolution, human burning of fossil fuels has raised atmospheric greenhouse gas (GHG) concentrations to dangerous levels. The latest Intergovernmental Panel on Climate Change (IPCC) report makes it clear that humans and anthropogenic emissions are the major causal factors behind the observed warming. In the face of the predicted challenges of a climate-disrupted world, many nations are looking to move away from fossil fuels. In particular, developing nations are looking to their rivers to supply a “clean” source of energy, secure water supplies, and otherwise provide security against the oncoming changes. While this is a laudable (and legitimate) goal, it is vital that the world refrain from proceeding on the basis of faulty premises.

A review of the latest scientific literature makes it clear that hydropower is not nearly as climate-friendly as has previously been assumed. Dam-based emissions mostly come in the form of methane from decomposition of organic matter, although carbon dioxide and nitrous oxide are also by-products of artificial reservoirs. Latitude, geography, and land use practices all contribute to the degree to which traditional, large-scale hydropower reservoirs contribute to GHG emissions. The majority of “untapped” hydropower sites lie in the tropics, which raises their initial methane emissions. Shallow-basin reservoirs contain more organic material, which also produces more methane. Industrial nitrogen fertilizers results in nitrogen saturation, which in turn increase nitrous oxide emissions. Likewise, a further net carbon increase accompanies the deforestation which results from reservoir creation. These factors combine to make extreme caution necessary before expanding hydroelectric generation, and suggest that alternative avenues of renewable energy would be preferable.

A better alternative would be decommissioning “traditional” hydropower in favor of run-of-the-river generation schemes, preventing new reservoir construction, and adopting sustainable land reclamation practices in the former inundation zones. There are existing technologies which could provide the power generation, water resource and flood control benefits of any decommissioned dams. These practices include reforestation efforts and establishment of riparian buffers, along with the use of carbon-aware agricultural practices. Presuming that the Reducing Emissions from Deforestation and forest Degradation Bali Action Plan (REDD+) can allow such efforts to be successful, the restoration of ecological flow in formerly disrupted habitat could pay additional “ecological services” dividends. Once fully reestablished, the new forest would also serve as an effective riparian buffer. By implementing or restoring a natural filter of vegetation around the global riverine system, we can deprive the methane-generating biological processes of source fuel, reducing the amount of methane production. If such a filter buffer consists of native primary-succession vegetation, a further reduction in net carbon could occur. Ultimately, the process of dam removal should lead to restoration of pre-inundation habitat, in order to maximize reduction of GHG emissions.

As reservoir infrastructure ages, the impounding dams become increasingly ripe for outright removal or redevelopment as small hydro plants. In determining priority removal projects, the international community should develop an ecological calculus. This calculus should include size, geophysical characteristics, latitude and age in determining which impoundment structures to target. The ecological removal calculus should also apply to the determination of Certified Emission Reductions. At a minimum, prevention of tropical reservoir creation and decommissioning dams which already exist would provide a significant reduction in anticipated GHG emissions. The REDD+ framework, once finalized, should provide those nations which choose to reduce their hydrological impacts incentive and aid to do so. In particular, REDD+ should encourage reforestation of former reservoir areas. In the alternative, the alluvial silt of the reservoir bottom would provide effectively “free” agricultural land, mitigating the need for additional deforestation. If a jurisdiction which decommissions a dam declines to restore the pre-inundation ecology, the basin should at least receive consideration as a potential cultivation site.

If countries refuse to consider these measures and insist on large-scale hydropower, they should at least be mindful of several things in their planning. First, the effects from the creation of any dam must be factored into the relevant carbon budget. Second, countries must adhere to their responsibilities under international instruments such as the Convention on Biological Diversity. Likewise, they must incorporate input from all relevant stakeholder groups, especially indigenous communities which will likely be displaced by reservoir creation. Finally, countries absolutely must incorporate solid ecological science and all available environmental mitigation measures to maintain “natural” ecological flows in their planning. Otherwise, they will end up exacerbating the damage caused by the creation of a new large-scale reservoir.

Click here to download Mr. English's full paper.